Purification and some properties of bovine pineal tryptophan 5-monooxygenase |
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Authors: | T Nukiwa C Toyama C Okita T Kataoka A Ichiyama |
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Affiliation: | Department of Physiological Chemistry and Nutrition Faculty of Medicine, University of Tokyo Hongo, Bunkyo-ku, Tokyo 113, Japan |
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Abstract: | Tryptophan 5-monooxygenase was purified approximately 1,000-fold from the bovine pineal gland. The purified enzyme catalyzed the hydroxylations of both L-tryptophan and L-phenylalanine at a comparable rate. Evidence was presented suggesting that the hydroxylations of both amino acids were catalyzed by the single enzyme. The apparent Km values for L-tryptophan and for L-phenylalanine were approximately 16 and 32 μM, respectively, when tetrahydrobiopterin was used as a cofactor. The apparent molecular weight of the enzyme was estimated to be approximately 30,000 by gel filtration on columns of Sephadex G-75 and G-100 and by ultracentrifugation in sucrose density gradients. These properties of bovine pineal tryptophan 5-monooxygenase were distinguishable from those of rat liver phenylalanine hydroxylase, another enzyme which had been shown to catalyze the hydroxylations of both L-tryptophan and L-phenylalanine. |
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